Anti-swelling hydrogel capable of quickly gelling and preparation method of anti-swelling hydrogel

Abstract

The invention relates to the field of anti-swelling hydrogel materials, and discloses a preparation method of anti-swelling hydrogel capable of rapidly gelling. Polyallylamine hydrochloride and acrylate are used as raw materials, persulfate is used as an initiator, N, N '-methylenebisacrylamide is used as a cross-linking agent, preparation of a polymer is realized by adopting a free radical polymerization method, construction of an elastic network is realized by utilizing electrostatic interaction and chemical cross-linking, and the dosage of the raw materials is optimized. Finally, the anti-swelling hydrogel capable of rapidly gelling is prepared, the gel forming speed is high, and water molecules are difficult to permeate into a network due to the compactness of the cross-linked network, so that the volume change of the hydrogel after water absorption is reduced, and the gel has anti-swelling performance.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and in particular to a preparation method of an anti-swelling hydrogel that can rapidly gel. Background Art

[0002] Hydrogels are highly water-containing polymers with a three-dimensional network structure and have been widely used in fields such as water retention and moisturization, biomedicine, sensing, and energy storage. However, the hydrophilicity of the hydrogel network structure causes the hydrogel to swell significantly after being immersed in water, thereby limiting its application in high-humidity environments or underwater engineering. Therefore, how to effectively inhibit the swelling of hydrogels has become a challenge.

[0003] Currently, certain progress has been made in the research on anti-swelling hydrogels. For example, Chinese Patent CN115651124A reports using chitosan molecular chains as the first network and butyl acrylate, 2-hydroxyethyl methacrylate, and acrylic acid as monomers to form the second network, and forming a double-network cross-linked structure through hydrogen bonding, which has good mechanical properties, high continuous conductivity, and anti-swelling properties; Chinese Patent CN114573748A uses alkyl acrylate, dimethylaminoethyl methacrylate, and 2-hydroxyethyl acrylate as raw materials. An underwater-adhesive and anti-swelling hydrogel is prepared by the method of preparing a precursor solution and then ultrasonic mixing; Chinese Patent CN116903883A obtains a gel prepolymer of chitosan, acrylic acid, and AlCl3, and after dissolution and standing, and irradiating with ultraviolet light for 1 h, a polyacrylic acid network gel is obtained, and an underwater anti-swelling strain sensor can be obtained by assembling with supporting equipment; Chinese Patent CN118165295A mixes an aqueous solution of polyvinyl alcohol and an ethylene-vinyl acetate copolymer emulsion evenly, forms a gel network through hydrogen bonding to obtain a copolymer mixture; then the copolymer mixture is cured in an alcohol solvent for 1 h to destroy the interaction of the polymer network and re-form a gel network with good mechanical properties, obtaining an anti-swelling hydrogel and an anti-swelling hydrogel tube.

[0004] However, the preparation methods involved in the existing reports are either relatively complex or require a long time to complete polymerization. For example, in Chinese Patent CN116903883A mentioned above, it takes two steps to obtain a hydrogel with target properties, which is time-consuming and requires reaction conditions of ultraviolet light irradiation. This limits the application of hydrogels in fields such as emergency medical treatment and environmental emergency handling, and it is difficult to achieve "ready-to-use immediately". Therefore, how to simply and quickly achieve rapid gelation and endow the hydrogel with excellent anti-swelling properties has become a worthy research work. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to develop an efficient preparation method of anti-swelling hydrogel, solve the problem that the hydrogel is easily swollen by water, achieve rapid gelation, and expand the application field of the hydrogel.

[0006] The technical solution adopted by the present invention is: to prepare a polymer by the method of free radical polymerization, and to construct an elastic network by using electrostatic interaction and chemical crosslinking, and finally obtain an anti-swelling hydrogel that can rapidly gel.

[0007] The main reactants used in the present invention include: polyallylamine hydrochloride, acrylate, persulfate and N,N''-methylenebisacrylamide.

[0008] The raw material composition components are calculated by weight mass parts and mainly include:

[0009]

[0010]

[0011] Among them, the molecular weight of polyallylamine hydrochloride is 15,000-20,000, and the molecular formula is (C3H7N) n .xHCl, which is an off-white powder and can be dissolved in water;

[0012] Among them, the acrylate includes sodium acrylate and magnesium acrylate, and sodium acrylate is preferred. The molecular formula of sodium acrylate is C3H3O2Na, which is a white powder and can be dissolved in water. The chemical formula of magnesium acrylate is C6H6MgO4, which is a white powder;

[0013] Among them, the persulfate is potassium persulfate K2S2O8 or ammonium persulfate (NH4)2S2O8, and potassium persulfate is preferred;

[0014] Among them, N,N'-methylenebisacrylamide is used as a crosslinking agent, and the molecular formula is C7H 10 N2O2.

[0015] Among them, as a preference, the mass ratio of polyallylamine hydrochloride to acrylate is 1:1. The addition amount of N,N'-methylenebisacrylamide is 0.5%-2.5% of the molar amount of acrylate.

[0016] The present invention provides a preparation method of an anti-swelling hydrogel that can rapidly gel, including the following steps:

[0017] Step 1: Preparation of the solution

[0018] Dissolve the polyallylamine hydrochloride powder in the raw materials in no less than 1.0 times the mass part of deionized water to prepare a component solution;

[0019] Step 2: Place the polyallylamine hydrochloride solution configured in Step 1 on a magnetic stirrer, add acrylate powder while stirring, add N,N'-methylenebisacrylamide (MBA) powder while stirring after 4 - 5 minutes, and add persulfate to initiate the polymerization reaction while stirring after 4 - 5 minutes to obtain a hydrogel.

[0020] Step 3: Immerse the hydrogel in deionized water for 30 - 90 min to remove chloride ions and sodium ions, obtaining a hydrogel with anti-swelling property.

[0021] In the polymerization reaction, potassium persulfate (KPS) has strong oxidizing property and is itself reduced, undergoing a reduction reaction. Polyallylamine hydrochloride hydrolyzes after dissolving in water, and -NH3 + in polyallylamine hydrochloride hydrolyzes to form -NH2, which has reducing property and forms a redox initiation system with KPS to generate free radicals, initiating the polymerization of sodium acrylate to form sodium polyacrylate. The amino cation (-NH3 + ) after polyallylamine hydrochloride dissolves in water and the carboxylate ion (-COO - ) of sodium polyacrylate form a stable network structure through electrostatic interaction. This electrostatic interaction is the key to the formation of the hydrogel, which enables the polymer chains to crosslink with each other to form a three-dimensional network; meanwhile, N,N'-methylenebisacrylamide acts as a crosslinking agent to form chemical crosslinks between polymer molecular chains, providing mechanical strength for the hydrogel.

[0022] The reason for the fast-gelling characteristic of this system is as follows: 1. After polyallylamine hydrochloride dissolves in water, -NH3 + hydrolyzes to form NH2, which is rich in reducing substances and can form a redox reaction with KPS to effectively initiate the polymerization of the system. 2. The polyanion formed by the polymerization of sodium acrylate and the polycation formed after polyallylamine hydrochloride dissolves in water form a crosslinked network through electrostatic interaction, enabling fast gelling.

[0023] Immerse the prepared hydrogel in deionized water for 1 h to remove chloride ions and sodium ions. This gel has the performance characteristic of anti-swelling. The reasons are as follows: 1. After the prepared hydrogel is immersed in water, chloride ions and sodium ions are free in the deionized water, and the effect of charge shielding is reduced. The amino group (-NH3 + ) after polyallylamine hydrochloride dissolves in water and the carboxylate group (-COO - ) of sodium polyacrylate form an electrostatic interaction through ionic crosslinking, and the hydrophobic alkyl long chains are exposed in water, reducing the hydrophilicity of the gel network and making the obtained crosslinked network denser. 2. The denseness of the crosslinked network makes it difficult for water molecules to penetrate into the network interior, thereby reducing the volume change of the hydrogel after water absorption and endowing the gel with anti-swelling property.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention prepares a swelling-resistant hydrogel that can rapidly gel through free radical polymerization. The operation is simple, ensuring the safety of the production process. The chemical reagents used in the present invention are all common polymer material monomers and initiators, with low toxicity and danger. In addition, the reaction conditions of the present invention are mild, without the need for complex equipment and harsh environmental requirements, making the entire preparation process cost low. Therefore, the preparation method of the present invention not only improves the preparation efficiency of the hydrogel, but also provides economic and safety guarantees for large-scale production and application.

[0026] (2) The swelling-resistant polyallylamine hydrochloride / acrylic acid hydrogel that can rapidly gel prepared by the present invention through free radical polymerization has a short gel time, about 1-7 minutes. After polyallylamine hydrochloride is dissolved in water in the present invention, -NH3 + hydrolyzes to form NH2, which is rich in reducing substances and can form a redox reaction with KPS to effectively initiate the polymerization of the system. In addition, the polyanion formed by the polymerization of acrylate and the polycation formed by polyallylamine hydrochloride dissolved in water form a cross-linked network through electrostatic interaction, which can rapidly gel; at the same time, the chemical cross-linked structure improves the mechanical strength of the hydrogel. This characteristic of rapid gelation makes the hydrogel have significant advantages in application scenarios that require rapid response, such as emergency medical treatment and environmental remediation, and can effectively shorten the treatment time and improve the application efficiency.

[0027] (3) The swelling-resistant polyallylamine hydrochloride / acrylic acid hydrogel that can rapidly gel prepared by the present invention through free radical polymerization has excellent swelling-resistant performance, and the volume change rate after immersion in water can be reduced to 0.21%. In the polymer network, the amino cation (-NH3 + ) of polyallylamine hydrochloride dissolved in water and the carboxylate ion (-COO-) of polyacrylate form an electrostatic interaction through ionic cross-linking, and the hydrophobic alkyl long chains are exposed in water, making the hydrophilicity of the gel network decrease, and the obtained cross-linked network is denser. At the same time, the denseness of the cross-linked network makes it difficult for water molecules to penetrate into the network interior, thereby reducing the volume change of the hydrogel after water absorption and making the gel have swelling-resistant performance. This excellent swelling-resistant performance makes the hydrogel show good stability and reliability in application scenarios such as high humidity environments or underwater engineering, and can effectively avoid structural damage and functional failure caused by swelling. Description of the Drawings

[0028] Figure 1 is the Fourier infrared spectrum of the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Example 3 after quenching and freeze-drying in liquid nitrogen;

[0029] Figure 2 It is a cross-sectional scanning electron microscope image of the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Example 4 and Example 8 after being quenched in liquid nitrogen and then freeze-dried.

[0030] Figure 3 It is a rheological gel time diagram of the polyallylamine hydrochloride / sodium acrylate hydrogel PAHx-SAy system.

[0031] Figure 4 It is about the polyallylamine hydrochloride / sodium acrylate hydrogel PAHx-SAy-MBA z％ system's rheological gel time diagram.

[0032] Figure 5 It is a modulus diagram of the polyallylamine hydrochloride / sodium acrylate hydrogel PAHx-SAy system.

[0033] Figure 6 It is about the polyallylamine hydrochloride / sodium acrylate hydrogel PAHx-SAy-MBA z％ system's modulus diagram.

[0034] Figure 7 It is a water content diagram of the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Examples 3-8.

[0035] Figure 8 It is a swelling ratio diagram of the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Examples 3-8.

[0036] Figure 9 It is a stress-strain curve diagram of the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Examples 4-7. Detailed implementation manners

[0037] The present invention is not limited to the following specific implementation manners. Those of ordinary skill in the art can implement the present invention in other various specific implementation manners according to the content disclosed in the present invention, or any simple changes or modifications made by adopting the design structure and idea of the present invention fall within the protection scope of the present invention.

[0038] The following relevant performance tests were carried out on the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in the following examples by the following methods:

[0039] 1. Rheological property test

[0040] Dynamic oscillation test: Using an MCR301 rotational rheometer, adopting a 25 mm plate mode with a plate gap of 1000 μm, the dynamic oscillation test was carried out under the conditions of a frequency of 1 Hz and a strain of 1% to obtain data of the elastic modulus and the viscous modulus through time scanning, and the corresponding test temperature was set at 25 °C.

[0041] 2. Moisture Content Test

[0042] The moisture content of polyallylamine hydrochloride / acrylic acid hydrogel with different solid contents was obtained by measuring the mass difference before and after water loss. Here, W0 represents the original mass value of the gel sample before water loss, and Wt represents the mass value of the gel after water loss. To ensure the accuracy of the test results, each sample was tested multiple times and the average value was taken. The polyallylamine hydrochloride / acrylic acid hydrogel was dried in a vacuum drying oven at a temperature of 80°C for 36 hours. The formula is as follows:

[0043]

[0044] 3. Swelling Ratio Test

[0045] The polyallylamine hydrochloride / acrylic acid hydrogel obtained from the reaction was dried on the surface at room temperature and then measured. The obtained volume was recorded as V0, that is, the initial volume. The polyallylamine hydrochloride / acrylic acid hydrogel was immersed in deionized water. After a certain period of time, the hydrogel was taken out, the excess water on the surface of the hydrogel was blotted dry with filter paper, and then the volume at this time was measured and recorded as V, that is, the real-time volume. When the continuous measurement of the real-time volume V of the hydrogel no longer changes, it is considered to reach the swelling equilibrium. To ensure the accuracy of the test results, each sample was tested multiple times and the average value was taken. The calculation formula S for the volume change rate of the hydrogel at this time is as follows:

[0046]

[0047] Looking at the absolute value of the volume change rate, the smaller the absolute value, the smaller the volume change and the better the anti-swelling performance.

[0048] 4. Mechanical Property Test

[0049] The strain and stress values of polyallylamine hydrochloride / acrylic acid hydrogel with different solid contents under a tensile speed of 100 mm / min were measured.

[0050] 5. Gel Time

[0051] The prepared solution was dropped onto the device of a rotary rheometer, and the oscillatory mode of the rotary rheometer was used for testing. The intersection point of the elastic modulus G’ and the viscous modulus G” was the gel time. Near the gel point, G’ and G” cross, which is a characteristic feature of the transition from liquid to solid. That is, when the elastic modulus and the viscous modulus are equal, it can be regarded as the gel time point.

[0052] In the following examples, unless otherwise specified, the component mass fractions and percentages involved are all mass fractions and mass percentages.

[0053] The present invention will be further described in detail below in conjunction with examples:

[0054] Example 1

[0055] Preparation of the solution: Dissolve 120 parts by mass of polyallylamine hydrochloride in 816 parts by mass of deionized water. Place the prepared polyallylamine hydrochloride solution on a magnetic stirrer, and while stirring, add 264 parts by mass of sodium acrylate powder. After 4 to 5 minutes, while stirring, add 1 part by mass of potassium persulfate solution to initiate the polymerization reaction. After 1 to 5 minutes, the polyallylamine hydrochloride / sodium acrylate hydrogel (PAH10-SA22) is prepared.

[0056] Performance test results

[0057] Immerse the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Example 1 in deionized water for 1 h to remove chloride ions and sodium ions. In the oscillatory test of a rotational rheometer, the gel time is measured to be 358 s, the water content is 60.13%, the volume change rate of the hydrogel on the first day of immersion in water is 0.88%, it reaches 2.53% on the 16th day, and -6.39% on the 30th day.

[0058] Example 2

[0059] Preparation of the solution: Dissolve 156 parts by mass of polyallylamine hydrochloride in 816 parts by mass of deionized water. Place the prepared polyallylamine hydrochloride solution on a magnetic stirrer, and while stirring, add 228 parts by mass of sodium acrylate powder. After 4 to 5 minutes, while stirring, add 1 part by mass of potassium persulfate solution to initiate the polymerization reaction. After 1 to 5 minutes, the polyallylamine hydrochloride / sodium acrylate hydrogel (PAH13-SA19) is prepared.

[0060] Performance test results

[0061] Immerse the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Example 2 in deionized water for 1 h to remove chloride ions and sodium ions. In the oscillatory test of a rotational rheometer, the gel time is measured to be 60 s, the water content is 50.77%, the volume change rate of the hydrogel on the first day of immersion in water is 3.82%, it reaches -8.28% on the 16th day, and -11.15% on the 30th day.

[0062] Example 3

[0063] Preparation of the solution

[0064] Dissolve 192 parts by mass of polyallylamine hydrochloride in 816 parts by mass of deionized water. Place the prepared polyallylamine hydrochloride solution on a magnetic stirrer, and while stirring, add 192 parts by mass of sodium acrylate powder. After 4 to 5 minutes, while stirring, add 1 part by mass of potassium persulfate solution to initiate the polymerization reaction. After 1 to 5 minutes, the polyallylamine hydrochloride / sodium acrylate hydrogel (PAH16-SA16) is prepared.

[0065] Performance test results

[0066] The polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Example 3 was immersed in deionized water for 1 h to remove chloride ions and sodium ions. In the oscillatory test of a rotational rheometer, the gel time was measured to be 109 s, the water content was 41.15%, the volume change rate of the hydrogel on the first day of immersion in water was 0.21%, reached 1.43% on the 16th day, and reached 1.18% on the 30th day.

[0067] Compared with Example 1, for the systems with a mass ratio of polyallylamine hydrochloride to sodium acrylate of 19:13, 22:10, and 25:07, with other operations the same as in Example 1, the hydrogels are designated as PAH19 - SA13, PAH22 - SA10, and PAH25 - SA07, and the hydrogel properties are shown in Table 2.

[0068] Example 4

[0069] Preparation of solution

[0070] 192 parts by mass of polyallylamine hydrochloride was dissolved in 816 parts by mass of deionized water. The prepared polyallylamine hydrochloride solution was placed on a magnetic stirrer, and while stirring, 192 parts by mass of sodium acrylate powder was added. After 4 to 5 minutes, while stirring, 1.57 parts by mass of the cross - linker N,N’ - methylenebisacrylamide (MBA) powder was added. After 4 to 5 minutes, while stirring, 1 part by mass of potassium persulfate solution was added to initiate the polymerization reaction. After 1 to 5 minutes, the polyallylamine hydrochloride / sodium acrylate hydrogel (PAH16 - SA16 - MBA 0.5％ ) was prepared.

[0071] Performance test results

[0072] The polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Example 4 was immersed in deionized water for 1 h to remove chloride ions and sodium ions. In the oscillatory test of a rotational rheometer, the gel time was measured to be 103 s, the water content was 43.21%, the volume change rate of the hydrogel on the first day of immersion in water was - 4.92%, reached - 7.36% on the 16th day, and reached - 3.27% on the 30th day.

[0073] Example 5

[0074] Preparation of solution

[0075] Dissolve 192 parts by mass of polyallylamine hydrochloride in 816 parts by mass of deionized water. Place the prepared polyallylamine hydrochloride solution on a magnetic stirrer, and while stirring, add 192 parts by mass of sodium acrylate powder. After 4 to 5 minutes, while stirring, add 3.15 parts by mass of crosslinking agent N,N''-methylenebisacrylamide (MBA) powder. After 4 to 5 minutes, while stirring, add 1 part by mass of potassium persulfate solution to initiate the polymerization reaction. After 1 to 5 minutes, polyallylamine hydrochloride / sodium acrylate hydrogel (PAH16-SA16-MBA 1％ ) is prepared.

[0076] Performance test results

[0077] Immerse the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Example 5 in deionized water for 1 h to remove chloride ions and sodium ions. The gel time is measured to be 96 s in the oscillatory test of a rotational rheometer, the water content is 50.50%, the volume change rate of the hydrogel on the first day of immersion in water is -9.13%, reaches -15.24% on the 16th day, and reaches -15.06% on the 30th day.

[0078] Example 6

[0079] Preparation of solution

[0080] Dissolve 192 parts by mass of polyallylamine hydrochloride in 816 parts by mass of deionized water. Place the prepared polyallylamine hydrochloride solution on a magnetic stirrer, and while stirring, add 192 parts by mass of sodium acrylate powder. After 4 to 5 minutes, while stirring, add 4.72 parts by mass of crosslinking agent N,N''-methylenebisacrylamide (MBA) powder. After 4 to 5 minutes, while stirring, add 1 part by mass of potassium persulfate solution to initiate the polymerization reaction. After 1 to 5 minutes, polyallylamine hydrochloride / sodium acrylate hydrogel (PAH16-SA16-MBA 1.5％ ) is prepared.

[0081] Performance test results

[0082] Immerse the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Example 6 in deionized water for 1 h to remove chloride ions and sodium ions. The gel time is measured to be 133 s in the oscillatory test of a rotational rheometer, the water content is 51.00%, the volume change rate of the hydrogel on the first day of immersion in water is -12.14%, reaches -20.25% on the 16th day, and reaches -20.5% on the 30th day.

[0083] Example 7

[0084] Preparation of solution

[0085] Dissolve 192 parts by mass of polyallylamine hydrochloride in 816 parts by mass of deionized water. Place the prepared polyallylamine hydrochloride solution on a magnetic stirrer, and while stirring, add 192 parts by mass of sodium acrylate powder. After 4 to 5 minutes, while stirring, add 6.29 parts by mass of crosslinking agent N,N''-methylenebisacrylamide (MBA) powder. After 4 to 5 minutes, while stirring, add 1 part by mass of potassium persulfate solution to initiate the polymerization reaction. After 1 to 5 minutes, polyallylamine hydrochloride / sodium acrylate hydrogel (PAH16-SA16-MBA 2％ ) is prepared.

[0086] Performance test results

[0087] Immerse the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Example 7 in deionized water for 1 h to remove chloride ions and sodium ions. The gel time is measured to be 115 s in the oscillatory test of a rotational rheometer, the water content is 57.36%, the volume change rate of the hydrogel on the first day of immersion in water is -11.58%, reaches -20.29% on the 16th day, and reaches -20.5% on the 30th day.

[0088] Example 8

[0089] Preparation of solution

[0090] Dissolve 192 parts by mass of polyallylamine hydrochloride in 816 parts by mass of deionized water. Place the prepared polyallylamine hydrochloride solution on a magnetic stirrer, and while stirring, add 192 parts by mass of sodium acrylate powder. After 4 to 5 minutes, while stirring, add 7.87 parts by mass of crosslinking agent N,N''-methylenebisacrylamide (MBA) powder. After 4 to 5 minutes, while stirring, add 1 part by mass of potassium persulfate solution to initiate the polymerization reaction. After 1 to 5 minutes, polyallylamine hydrochloride / sodium acrylate hydrogel (PAH16-SA16-MBA 2.5％ ) is prepared.

[0091] Performance test results

[0092] Immerse the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Example 8 in deionized water for 1 h to remove chloride ions and sodium ions. The gel time is measured to be 79 s in the oscillatory test of a rotational rheometer, the water content is 55.01%, the volume change rate of the hydrogel on the first day of immersion in water is -13.18%, reaches -20.76% on the 16th day, and reaches -22.48% on the 30th day.

[0093] Example 9

[0094] Preparation of solution

[0095] Dissolve 192 parts by mass of polyallylamine hydrochloride in 816 parts by mass of deionized water. Place the prepared polyallylamine hydrochloride solution on a magnetic stirrer, and while stirring, add 192 parts by mass of sodium acrylate powder. After 4 to 5 minutes, while stirring, add 1 part by mass of ammonium persulfate solution to initiate the polymerization reaction. After 1 to 5 minutes, polyallylamine hydrochloride / sodium acrylate hydrogel is prepared.

[0096] Performance test results

[0097] Immerse the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Example 9 in deionized water for 1 h to remove chloride ions and sodium ions. The gel time is measured to be 360 s in the oscillatory test of a rotational rheometer, the water content is 75.28%, the volume change rate of the hydrogel on the first day of immersion in water is -8.43%, and it reaches -15.22% on the 3rd day.

[0098] It can be seen from Example 9 that by changing the initiator to ammonium persulfate, the prepared hydrogel also has the properties of rapid gelation and anti-swelling, but the effect is not as good as that of potassium persulfate.

[0099] Example 10

[0100] Preparation of solution

[0101] Dissolve 192 parts by mass of polyallylamine hydrochloride in 816 parts by mass of deionized water. Place the prepared polyallylamine hydrochloride solution on a magnetic stirrer, and while stirring, add 340 parts by mass of magnesium acrylate powder. After 4 to 5 minutes, while stirring, add 1 part by mass of potassium persulfate solution to initiate the polymerization reaction. After 1 to 5 minutes, polyallylamine hydrochloride / magnesium acrylate hydrogel is prepared.

[0102] Performance test results

[0103] Immerse the polyallylamine hydrochloride / magnesium acrylate hydrogel prepared in Example 10 in deionized water for 1 h to remove chloride ions and sodium ions. The gel time is measured to be 420 s in the oscillatory test of a rotational rheometer, the water content is 49.26%, the volume change rate of the hydrogel on the first day of immersion in water is -2.31%, and it reaches 1% on the 3rd day.

[0104] It can be seen from Example 10 that by changing the acrylate to magnesium acrylate, the prepared hydrogel also has the properties of rapid gelation and anti-swelling.

[0105] Comparative Example 1

[0106] Compared with Example 8, the difference in Comparative Example 1 is that the MBA crosslinking agent is replaced with AGE (allyl glycidyl ether), and other operations are the same as those in Example 8.

[0107] Performance test results:

[0108] The polyallylamine hydrochloride / magnesium acrylate hydrogel prepared in Comparative Example 1 was immersed in deionized water for 1 h to remove chloride ions and sodium ions. In the oscillatory test of a rotational rheometer, the gel time was measured to be 156 s, the water content was 65.72%, the volume change rate of the hydrogel on the first day of immersion in water was 14.20%, and it reached 16.87% on the 3rd day.

[0109] As can be seen from Comparative Example 1, the anti-swelling performance of the AGE cross-linking agent is inferior to that of the MBA cross-linking agent.

[0110] Systems with mass ratios of polyallylamine hydrochloride to sodium acrylate of 7:25, 10:22, 13:19, 16:16, 19:13, 22:10, and 25:07 were respectively labeled as PAH07-SA25, PAH10-SA22, PAH13-SA19, PAH16-SA16, PAH19-SA13, PAH22-SA10, and PAH25-SA07. When the cross-linking agent N,N'-methylenebisacrylamide (MBA) was added to the system, the molar percentages of MBA in the acrylate were 0.5%, 1%, 1.5%, 2%, and 2.5% respectively. The obtained PAHx-SAy-MBAz hydrogels were respectively labeled as

[0111] PAH16-SA16-MBA 0.5％ 、PAH16-SA16-MBA 1％ 、PAH16-SA16-MBA 1.5％ 、PAH16-SA16-MBA 2％ 、PAH16-SA16-MBA 2.5％ , and the specific mass fractions are shown in Table 1 below.

[0112] Table 1 Formulation of PAHx-SAy-MBAz hydrogel

[0113]

[0114]

[0115] Table 2 Performance parameters of PAHx-SAy-MBAz hydrogel

[0116]

[0117] Figure 1 It is the Fourier infrared spectrum of the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Example 3 after being quenched and then freeze-dried in liquid nitrogen. From Figure 1 it can be seen that the peak at 1623 cm of PAH -1 is the in-plane bending vibration peak of N-H, and the peak at 1523 cm -1is the out-of-plane bending vibration peak of N-H. SA shows peaks at 1641 cm -1 and 1585 cm -1 which are the asymmetric and symmetric stretching vibration peaks of C=O in -COO - , and they are the characteristic peaks of SA. From the infrared spectra of PAH22-SA-10, PAH10-SA22, and PAH16-SA16, it can be seen that there are amino absorption peaks, indicating that the gel contains polycations provided by PAH; at the same time, superimposed broad peaks are formed near 1645 - 1523 cm -1 , proving that the N-H deformation vibration peak and C=O stretching vibration peak in PAH participate in the formation of the gel network.

[0118] Figure 2 are the cross-sectional scanning electron microscope images of the polyallylamine hydrochloride / sodium acrylate hydrogels prepared in Example 4 and Example 8 after quenching and freeze-drying in liquid nitrogen. It can be seen from the figure that the hydrogel network presents a porous network structure. This is because a three-dimensional network structure has been formed in the gel network, so the pores are relatively dense and uniform. Comparing the SEM images of PAH16-SA16-MBA 0.5％ and AH16-SA16-MBA 2.5％ , it can be seen that the higher the content of MBA, the denser the pores. This is because with the increase of MBA, the covalent cross-linking between molecular chains causes the polymer molecular chains to cross-link together, further reducing the pore size, so the network structure is denser.

[0119] Figure 3 and Figure 4 are the rheological gel time diagrams of the polyallylamine hydrochloride / sodium acrylate hydrogels prepared in Examples 1 - 8. The storage modulus G' represents the elastic modulus of the material and is also called a measure of elastic solid behavior. The loss modulus G'' represents the viscous modulus of the material and is also called a measure of viscous liquid behavior. Figure 3 . Rheological gel time diagrams of PAHx-SAy (a) PAH07-SA25 (b) PAH10-SA22 (c) PAH13-SA19 (d) PAH16-SA16

[0120] (e) PAH19-SA13 (f) PAH22-SA10 (g) PAH25-SA07

[0121] From Figure 3It can be seen that the gelation times of PAH10-SA22, PAH13-SA19, PAH16-SA16, PAH19-SA13, and PAH22-SA0 are 358 s, 60 s, 109 s, 352 s, and 1413 s respectively. Therefore, it can be known that the closer the ratio of PAH to SA, the shorter the gelation time. Because when the ratio of PAH and SA is close, the charges between them can be better neutralized, forming more ionic bond cross-linking points. This charge neutralization effect promotes the cross-linking between polymer chains, thus accelerating the formation of the gel. And when the ratio of PAH to SA is close, it means that the number of positive and negative charges in the system is relatively balanced. This balance helps to more effectively form a three-dimensional network structure, reducing the time required to reach the gel state. When the mass ratio of PAH is much lower than SA, the gelation time is longer. When the mass ratio of PAH is much higher than SA, the gelation time is the longest.

[0122] Figure 4 is PAHx-SAy-MBA z％ rheological gelation time diagram of (a) PAH16-SA16-MBA 0％ (b) PAH16-SA16-MBA 0.5％ (c) PAH16-SA16-MB A 1％ (d) PAH16-SA16-MBA 1.5％ (e) PAH16-SA16-MBA 2％

[0123] (f) PAH16-SA16-MBA 2.5％ ; from Figure 4 it can be known that PAH16-SA16-MBA 0％ 、PAH16-SA16-MBA 0.5％ 、PAH16-SA16-MBA 1％ 、PAH16-SA16-MBA 1.5％ 、PAH16-SA16-MBA 2％ 、PAH16-SA16-MBA 2.5％ have gelation times of 109 s, 103 s, 96 s, 133 s, 115 s, and 79 s respectively. The gelation times after adding MBA do not vary much, indicating that the content of MBA has little effect on the gelation time of the PAH16-SA16 system.

[0124] Figure 5 and Figure 6 are the modulus diagrams of the polyallylamine hydrochloride / sodium acrylate hydrogels prepared in Examples 1-8. Through Figure 5From the modulus diagram of the PAHx-SAy system, it can be determined that the optimal ratio of PAH to SA is PAH16-SA16. At this ratio, the gel exhibits the best elasticity and stability because the positive and negative charge electrostatic balance is achieved at this ratio. The greater the difference in the ratio of PAH to SA, the more the charge balance is disrupted, and thus the modulus decreases.

[0125] Figure 6 In the PAHx-SAy-MBAz% system, the storage modulus decreases with the increase in the content of the molar ratio of the crosslinking agent MBA. This is because MBA can crosslink molecular chains, and due to the steric hindrance effect, the electrostatic interaction between molecular chains is weakened, so the modulus shows a decreasing trend.

[0126] Figure 7 It is the water content diagram of the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Examples 3-8. The closer the ratio of PAH to SA, the lower the water content. This is because when the ratio of PAH to SA is close, it means that the charge balance of anions and cations in the gel network is better, which helps to form a more uniform and dense network structure. The dense network crosslinking structure can more effectively limit the entry of water molecules, thereby reducing the water content of the gel.

[0127] With the increase in the content of the molar percentage of the crosslinking agent MBA, the water content of the hydrogel increases. As the content of MBA increases, the steric hindrance effect brought by chemical crosslinking weakens the electrostatic interaction between molecular chains to a certain extent. Thus, more free spaces are formed, and these free spaces can be occupied by water molecules, resulting in an increase in water content.

[0128] Figure 8 It is the swelling ratio diagram of the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Examples 3-8. It can be seen that almost no swelling occurs in all systems. With the increase in the amount of MBA added, the hydrogel will undergo a certain volume shrinkage. The reason is that the dense ionic crosslinking endows the network with excellent anti-swelling properties. After adding MBA, the steric hindrance effect brought by chemical crosslinking will hinder the escape of free ions. Therefore, during the immersion process, the molecular chains gradually approach as the concentration of free ions gradually decreases, resulting in the phenomenon of volume shrinkage.

[0129] Figure 9 It is the stress-strain curve diagram of the polyallylamine hydrochloride / sodium acrylate hydrogel prepared in Examples 4-7. The tensile strength and elongation at break of the PAH16-SA16-MBA 0.5％ hydrogel reach 96 KPa and 2221% respectively, and the tensile strength and elongation at break of the PAH16-SA16-MBA 1％ hydrogel reach 128 KPa and 1676% respectively. The PAH16-SA16-MBA 1.5％The tensile strength and elongation at break of the hydrogel reached 133 KPa and 898% respectively. PAH16-SA16-MBA 2.0％ The tensile strength and elongation at break of the hydrogel reached 95 KPa and 468% respectively. The tensile strength and elongation at break of the PAH16-SA16 hydrogel reached 81 KPa and 2327% respectively. As can be seen from the figure, the addition of MBA significantly improved the tensile strength of the hydrogel.

[0130] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rapidly gellable anti-swelling hydrogel, characterized in that: The composition components of the anti-swelling hydrogel raw materials are calculated by weight parts and include: 84-300 parts of polyallylamine hydrochloride, 84-340 parts of acrylate, 800-820 parts of deionized water, 0.8-1.2 parts of persulfate, and 0-7.9 parts of N,N'-methylenebisacrylamide.

2. The quickly gellable and anti-swelling hydrogel according to claim 1, wherein: The molecular weight of polyallylamine hydrochloride is 15,000-20,000.

3. The quickly gellable anti-swelling hydrogel according to claim 1, characterized in that: The persulfate is potassium persulfate or ammonium persulfate.

4. The quickly gellable and anti-swelling hydrogel according to claim 1, characterized in that: The acrylate is sodium acrylate or magnesium acrylate.

5. The quickly gellable and anti-swelling hydrogel according to claim 1, characterized in that: The persulfate is potassium persulfate and the acrylate is sodium acrylate.

6. The quickly gellable and anti-swelling hydrogel according to claim 1, characterized in that: The mass ratio of polyallylamine hydrochloride to acrylate is 1:

1.

7. The quickly gellable anti-swelling hydrogel according to claim 1, characterized in that: The addition amount of N,N'-methylenebisacrylamide is 0.5%-2.5% of the molar amount of acrylate.

8. The preparation method of the quickly gellable anti-swelling hydrogel according to any one of claims 1-7, characterized in that: Step 1: Dissolve polyallylamine hydrochloride powder in deionized water to prepare a polyallylamine hydrochloride solution; Step 2: Place the polyallylamine hydrochloride solution in Step 1 on a magnetic stirrer, add acrylate powder while stirring, add crosslinking agent N,N'-methylenebisacrylamide powder while stirring after 4-5 minutes, and add persulfate while stirring after 4-5 minutes to initiate a polymerization reaction to obtain a polyallylamine hydrochloride / sodium acrylate hydrogel; Step 3: Immerse the hydrogel in deionized water for 30-90 min to obtain an anti-swelling hydrogel.

Images